1H-pyrazolo[1,5-b][1,2,4]triazole coupler and 1H-pyrazolo[3,2-c][1,2,4]triazole coupler are excellent in spectral absorption characteristics compared with 5-pyrazolone couplers, and therefore are used in some color photographic materials. However, the light-fastness of the magenta dye image formed from these couplers is still not satisfactory when the coupler is used alone, and therefore further improvement thereof is desired.
Thus, attempts to enhance the light-fastness of image dyes by combining the above pyrazolotriazole couplers with various antioxidants have been proposed, for example, in U.S. Pat. No. 4,588,679 and JP-A ("JP-A" means unexamined published Japanese patent application) No. 262,159/1985. An attempt to improve the light-fastness of image dyes by combining the above pyrazolotriazole couplers with a metal complex has been made, as known from U.S. Pat. No. 4,590,153. Attempts to improve the light-fastness of image dyes by combining the above pyrazoloazole couplers with amine compounds, as described in JP-A Nos. 246052/1987 and 95,439/1988, have also been proposed.
On the other hand, various interesting behaviors have been found by the studies of dyes derived from the pyrazoloazole series coupler. That is, for example, these dyes are liable to aggregate and the dyes aggregated are more liable to be decomposed by the irradiation of light than those not aggregated. An invention to improve the light-fastness of image dye by changing the structure of coupler molecule has been made by utilizing this finding inversely. That is, JP-A No. 65,245/1986 discloses that the light-fastness of image dyes of couplers having an alkyl group directly connected through the secondary or the tertiary carbon atom to the skeleton of a pyrazoloazole coupler is remarkably improved.
Although these proposals much improve the light-fastness of image dyes, development of a further new technique for improving the light-fastness is greatly desired in color photography wherein image dyes are ideally required not to change permanently.